The invention is based on a wiper system drive apparatus comprising a wiper motor, a lever drive mechanism connected with a wiper of the wiper system and a coupling mechanism connecting the wiper motor with the lever drive mechanism in order to drive the wiper with the wiper motor.
Wiper systems with multiple windshield wipers for motor vehicles are fastened by their wiper bearings directly or indirectly via a mounting plate to the vehicle body. The mounting plate or a tubular mounting platexe2x80x94if the wiper carrier also includes tubular hollow profilesxe2x80x94includes a motor mounting plate, which carries a wiper drive with a wiper motor and a drive mechanism mounted thereon. A power takeoff shaft of the drive mechanism is mounted in a drive dome and, as a rule via a crank and joint rods, drives further cranks, which are rigidly connected to the drive shafts of the windshield wipers.
It is also possible for the power takeoff shaft of the wiper motor to drive a four-bar lever drive mechanism. This drive mechanism has a drive lever, which is pivotally mounted on a drive axle and is connected in articulated fashion to a guide rod lever via a coupling rod. This lever is pivotally supported on a stationary shaft. A fastening part of a wiper arm is formed integrally onto the coupling rod and with It forms a so-called four-bar wiper lever, to which the joint part of the wiper arm is fastened via a foldaway joint. The drive lever can be driven directly from a power takeoff shaft of the wiper motor or via a crank and joint rods. It can also be embodied as a cross lever. The kinematics of the four-bar lever mechanism effect a combined reciprocating and swiveling motion of the windshield wiper. As a result, the windshield wiper is better able to follow the angular contour of a vehicle window. If two synchronized windshield wipers are provided, then as a rule only one is driven via a four-bar lever mechanism, while the other is connected to a driven element, via a joint rod and a crank.
So that the forces on the joint rods will be slight, the crank has a relatively great length. This means a long radius of the crank path, which together with the typically low ratio of the crank radius to the rod length of approximately 1/4 to 1/7 demands a correspondingly large structural volume and associated room to move for the wiper linkage. Furthermore, it leads to an inharmonious course of motion. Wiper drives with reversible wiper motors are also known, In which the crank on the power takeoff shaft of the wiper motor executes a virtually semicircular pivoting motion. This drive requires markedly less room to move for the crank on the wiper motor.
In the known drives, the position of the wiper motor determines the location and geometry of the drive curve for the joint rods. Since the wiper motor and the lever drive mechanism cannot be positioned arbitrarily however, because the space in the vehicle is limited and is used for other equipment, the result is often unfavorable kinematics, which leads to an unfavorable course of speed and acceleration for the lever mechanism and as a rule requires a large amount of room to move. The result is compromises, which adversely affect the quality and reliability of the wiper system.
From European Patent Disclosure EP 0 781 691 A1, a wiper drive is known that comprises a wiper motor and a lever drive mechanism. An offset-bent drive crank is seated on the power takeoff shaft of the wiper motor. A joint rod, which is pivotally connected to the drive crank via a ball joint, is also pivotally connected by Its free end, again via a ball joint, to a crank embodied as a crank plate, which is fastened to a drive shaft of a windshield wiper. Via a further ball joint, the crank plate is engaged by a second joint rod, which with its free end is pivotally connected to a crank that is fastened to a drive shaft for a second windshield wiper. The lever mechanism comprising cranks and joint rods is very complicated and requires a great amount of room to move.
According to the invention, a coupling rod, which is pivotally connected to a guide rod pivotally supported on a vehicle body, is connected in articulated fashion to a crank; the thus-formed coupling mechanism is connected to the lever drive mechanism via a joint rod. The coupling mechanism, which In particular requires only little, compact room for motion, If a reversible wiper motor is used, offers many opportunities for pivotally connecting the joint rods and driving them. Thus the kinematics of the wiper drive can be varied such that by the selected articulated connection of the joint rods to the coupling mechanism, an unfavorable position of the wiper motor can be compensated for. As a result, the position of the wiper motor can be selected freely in accordance with the space available in the vehicle, without having to accept the above-described disadvantages Into the bargain.
The coupling rod can be a simple sheet-metal part, which on each of its ends has a joint pin that is adjoined by the guide rod and the crank, respectively, via a bearing shell. The joint pins can be fastened unilaterally to the coupling rod. To avoid bending forces at the attachment points between the joint pins and the coupling rod, it is expedient that the coupling rod have two sheet-metal parts, between which it retains at least one joint pin on its face ends. Because of the two-sided fastening of the joint pins and the bearing of the crank or guide rod between the fastening points, the bending forces are very slight.
If the crank, coupling rod and guide rod are located in the same plane, the joint pins can be embodied cylindrically. If not, ball joints can be provided instead. If the joint pins are fastened to the coupling rod on both of their face ends, then the coupling rod has a considerable height in the region of the joints. It is therefore advantageous to design the coupling rod in forked fashion on its ends, and it retains the joint pin in the fork. As a result it can assume an arbitrary height between the joints, so that in the case of a shallow design of the coupling rod, freedom of motion for the levers and articulation points is assured. This kind of design is suitable both for die-cast coupling rods and for coupling rods made of sheet-metal parts.
If the coupling rod has two sheet-metal parts, then the sheet-metal parts are expediently tacked together locally between the joint pins. One sheet-metal part can be curved toward the other, so that because of the offset bending of the sheet-metal part in the longitudinal direction of the coupling rod, free room to move is obtained for further drive parts. The coupling rod can also have offset bends transversely to the direction of motion, which assure freedom of motion for other drive parts.
The joint rods can be pivotally connected at various points of the coupling gear. This purpose is served by ball pegs, which are disposed for Instance on the crank of the wiper-motor, on the guide rod, on the coupling rod between the joints, or at the joint pins. If the ball pegs are disposed on the crank of the wiper motor or on the coupling rod or on the guide rod, then typically they are secured by wobble riveting. If the coupling rod, is locally tacked together between the joint pins, this can also be done by means of a ball peg which joins the two sheet-metal parts to one another in this region by wobble riveting.
A plurality of windshield wipers, as a rule two, can be driven via the coupling gear. In that case, many ball pegs should be provided, which can also be embodied as double-ball pegs.